Let there be lights!

Car headlamps have come a long way since they lit up the road ahead with tungsten filament bulbs that almost seem primitive by today’s standards. Let’s take a look at the different types of car headlights.

Incandescent

The early cars used incandescent light bulbs that had a filament made of tungsten, but were more powerful than the average house light bulb. Such bulbs work through the electric current heating up the filament and making it glow. The thicker the tungsten, the longer the bulb life. But the thinner the filament, the brighter the light.

Halogen

New technology applied to the tungsten filament gave us halogen lights. Halogen bulbs also require a tungsten filament, but are more efficacious producers of light as they use a thinner wire that offers a brighter white light. The bulb is filled with halogen gas that extends the life of the filament.

HID (xenon)

HID, or high-intensity discharge, headlamps are also known as xenon headlights because of the xenon gas used in the lamps. This type of headlamp doesn’t use a filament, but instead contains two electrodes in a xenon gas-sealed bulb. An electrical arc between the electrodes produces light that is almost three times brighter than a halogen bulb, and can last 10 times longer while using less energy.

HID headlamps lamps generate different-coloured light based on the temperature. As it gets hotter, it changes from yellow, to white, to bluish white. The downside to HID headlamps is that they can blind an oncoming driver with their high intensity and glare. Nevertheless, they have been proven to improve visibility.

On Singapore roads, vehicles with factory-fitted HID headlamp systems must incorporate an auto-altering or levelling feature, which automatically adjusts the headlamp angle and direction based on road and driving conditions, to minimise glare.

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In general, retrofitting of HID lamp systems on existing vehicles is not allowed because it would require the entire headlamp assembly, including the electrical system, to be replaced as the reflectors and lenses are different from those in a conventional halogen headlamp. In addition, the wiring would not be able to handle the much higher starting current required for a HID headlamp system.

LED

Light-emitting diodes (LEDs) have been undergoing very active development in the past few years for automotive use. LED bulbs use less power, produce whiter light and provide a much longer life than standard bulbs, but there are limitations due to cost and other factors.

They are increasingly used for a car’s signal functions such as parking lamps, brake lights, turn signals, as well as internal lighting. These applications offer significant advantages as they pose fewer engineering challenges than using them for headlamps.

LEDs are commonly considered to be low-heat devices since they are mostly used in areas that require only a small amount of light. But in fact, LEDs produce a significant amount of heat at the rear end of the emitters. They can also be damaged by high temperatures, and prolonged usage above the maximum temperature will ultimately shorten the device's lifespan.

As LED technology continues to evolve, the performance of LED headlamps is predicted to improve, and perhaps surpass, that of HID headlamps.